1. Field of the Invention
This invention relates to diapers equipped with a wetness monitoring system.
2. Description of the Prior Art
Babies and incontinent adults need to have their diapers changed when they are wet and soiled, not only for hygienic reasons, but to prevent diaper rash, dermatitis and ulcerations which can lead to serious infections.
Various types of diaper wetness monitors have previously been disclosed. For example, U.S. Pat. No. 4,356,818 to Macias et. al. describes an electric moisture-sensing disposable diaper having a liquid impervious outer sheet, a liquid permeable inner lining, and a moisture absorbing wadding associated with one or two strips of electrically conductive material. The presence of moisture produces an electrical short circuit which activates an alarm device.
U.S. Pat. No. 4,212,295 to Snyder discloses a moisture-responsive pad for treatment of enuresis. The pad employs two conductive outer layers separated by a non-conductive central layer, and is not adapted for use inside a disposable diaper.
U.S. Pat. No. 4,205,672 concerns a sensing device employing a conductive layer within a diaper. The baby""s skin serves as a second conductor. A signalling device is activated when the conductors are short-circuited by urine.
U.S. Pat. No. 4,191,950 describes a sensor consisting of a double strip of specially manufactured conductive vinyl cloth connected to specialized silver-impregnated Velcro fasteners. The sensor is designed to survive repeated laundering, and is intended primarily as an anti-bed-wetting device to train enuretic children to overcome bed wetting.
U.S. Pat. No. 4,539,559 to Kelly et. al. discloses a disposable warning device for detecting urine-wet undergarments. It employs a disposable sensor circuit having separated electrical terminals which may be printed on an absorbent pad. Its voltage source may be a 9 volt battery. Current passes between said terminals when wet with urine. The requisite operational current may produce discomfort to the wearer.
The moisture-detecting devices of the aforesaid Patents are of questionable reliability because they rely on the conductivity of the wetting substance itself (urine or other liquid wastes) in order to function properly. The problem with this is that there is high variability in the conductive efficiency of these fluids. Their conductance varies not only with the concentration of the dissolved solutes but also with the degree to which these substances are converted to their ionized forms. The colloidal or semi-colloidal nature of urine also affects its conductance. Thus, when the urine is highly dilute its conductance is reduced to nearly that of water, making it less reliable for activating these devices.
It is accordingly an object of the present invention to provide a wetness monitoring system suitable for use in disposable pediatric and adult diapers.
It is another object of this invention to provide a monitoring system as in the foregoing object which can reliably detect diaper wetness regardless of the conductance of the urine or other liquid bodily waste.
It is a further object of the present invention to provide a monitoring system of the aforesaid nature whose voltage requirement is sufficiently low so as to avoid discomfort or injury to the patient.
It is a still further object of this invention to provide a monitoring system of the aforesaid nature amenable to sufficiently low cost manufacture as to be commercially suitable for integration into disposable diapers, or for retrofitting into standard commercially available diapers.
Yet another object of the present invention is to provide a monitoring system of the aforesaid nature which enables a remotely stationed caregiver or supervisor to be aware not only of the status of the diaper but also of the timing and frequency of diaper changes and to have an automatic and permanent record of the same.
These objects and other objects and advantages of the invention will be apparent from the following description.
The above and other beneficial objects and advantages are accomplished in accordance with the present invention by a wetness monitoring system for a disposable diaper comprising:
a) a compliant sensor installable within the front center portion of said diaper and comprised of an inner conductive layer, a hydrophilic porous middle layer containing a water-soluble ionizable salt, and an outer conductive layer, said layers being non-conductively interconnected at discontinuous sites, said sensor being elongated between a lower extremity, and an upper extremity providing connection terminals,
b) a source of low voltage direct current electricity, and
c) an alarm pack containing electrically activatable alarm means and electrical circuitry interactive between said terminals, electricity, and alarm means, whereby
d) said middle layer, when contacted by urine, releases said salt to form a highly conductive volume of solution that produces an electrical short circuit between said inner and outer layers to activate said alarm means.
A telemetry sender unit may be interactively associated with said alarm pack to produce a recordable signal at a distant location.